In the communication system, a mobile station (MS) should have a connection set up to a base station (BS) in order to communicate with the BS. To identify each connection to the BS, the MS is assigned a CID from the BS. The MS, during its initial access to the network of the communication system, is assigned a basic CID and a primary management CID from the BS in order to exchange control data, or control signals, with the BS. In addition, the MS is assigned a transport CID for user data exchange.
That is, the transport CID is assigned to each connection on a one-by-one basis. Therefore, one MS may use a plurality of transport CIDs. Meanwhile, CIDs used in the communication system have, for example, a 16-bit size, and can be classified into various types according to their uses, and uses of the CIDs are shown in Table 1.
TABLE 1CIDValueDescriptionInitial Ranging0x0000Used by SS and BS during initialCIDranging process.Basic CID0x0001-mThe same value is assigned to boththe DL and UL connections.Primaryn + 1-2mThe same value is assigned to bothmanagementthe DL and UL connections.Transport2m + 1-FE9FFor the secondary managementCIDs,connection, the same value isSecondary Mgtassigned to both the DL and ULCIDsconnections.Multicast CIDs0xFEA0-0xFEFEFor the downlink multicastservice, the same value isassigned to all MSs on the samechannel that participate in thisconnection.AAS initial0xFEFFA BS supporting AAA shall use thisranging CIDCID when allocating an AAS rangingperiod (using AAS rangingallocation IE).Multicast0xFF00-0xFFC9A BS may be included in one or morepolling CIDsmulticast polling groups for thepurposes of obtaining bandwidthvia polling. These connectionshave no associated service flow.Normal mode0xFFFAUsed in DL-MAP to denote burstsmulticast CIDfor transmission of DL broadcastinformation to normal mode MS.Sleep mode0xFFFBUsed in DL-MAP to denote burstsmulticast CIDfor transmission of DL broadcastinformation to Sleep mode MS. Mayalso be used in MOB-TRF-INDmessages.Idle mode0xFFFCUsed in DL-MAP to denote burstsmulticast CIDfor transmission of DL broadcastinformation to Idle mode MS. Mayalso be used in MOB_PAG-ADVmessages.Fragmentable0xFFFDUsed by the BS for transmissionBroadcast CIDof management broadcastinformation with fragmentation.The fragment sub header shall use11-bit long FSN on thisconnection.Padding CID0xFFFEUsed for transmission of paddinginformation by SS and BS.Broadcast CID0xFFFFUsed for broadcast informationthat is transmitted on a downlinkto all SSs.
Various types of CIDs used in the communication system are shown in Table 1, and they can be classified into ranging CID, basic CID, primary management CID, transport CID, multicast CID, adaptive antenna system (AAS) initial ranging CID, multicast polling CID, normal mode multicast CID, sleep mode multicast CID, idle mode multicast CID, fragmentable broadcast CID, padding CID and broadcast CID according to their uses.
In addition, the BS can assign basic CID, primary management CID, transport CID, multicast CID and multicast polling CID to each MS. Among the CIDs, the multicast CID and multicast polling CID are assigned in common to a plurality of MSs. However, the basic CID and primary management CID are uniquely assigned to every MS.
The ranging CID is a CID used when an MS accesses a BS and attempts initial ranging.
The basic CID and primary management CID are CIDs that each MS is basically assigned from a BS when it accesses the BS. The multicast polling CID is a CID that predetermined particular MSs use in common. Padding CID is a CID that MSs and BS use in common to indicate ‘Padding’. Broadcast CID is a CID that the BS uses to notify MSs that a message including the corresponding CID is a broadcast message.
Generally, the CID assigned from the BS to the MS has a unique value within one BS, and if the MS moves from a service area of the BS to a service area of another BS, the MS should be assigned a new CID from the new BS.
Thereafter, during handover due to the change in the service access point of the MS, the BS and the MS exchange the basic CID and primary management CID with each other, as follows.
FIG. 1 is a signaling diagram illustrating CID transmission/reception in a general communication system. In the case shown herein, an MS is assumed to perform handover.
Referring to FIG. 1, the communication system includes an MS 110, a first BS 120 and a second BS 130. It will be assumed that the first BS 120 is a serving BS which is now providing a communication service to the MS 110, and the second BS 130 is a target BS to which the MS 110 will perform handover.
In step 111, the first BS 120 transmits a downlink channel descriptor (DCD) message to the MS 110. The DCD message is a message broadcasted by the first BS 120.
In step 113, upon receipt of the DCD message, the MS 110 transmits a ranging-request (RNG-REQ) message to the first BS 120. The MS 110 delivers the basic information for a call connection to the first BS 120 through the RNG-REQ message.
In step 115, the first BS 120 transmits a ranging response (RNG-RSP) message to the MS 110 in response to the RNG-REQ message. In this case, the first BS 120 transmits a basic CID to the MS 110 along with the RNG-RSP message to exchange control signals for an initial access. For example, the basic CID is assumed to be ‘10’. The MS 110 performs synchronization acquisition and transmission power control operations with the first BS 120 by performing the ranging operation of steps 113 through 115.
In step 117, the MS 110 transmits a subscriber station basic capability request (SBC-REQ) message to the first BS 120 for basic capacity negotiation with the first BS 120. The SBC-REQ message includes information on a modulation scheme and/or coding scheme available to the MS 110.
In step 119, the first BS 120 transmits a subscriber station basic capability response (SBC-RSP) message to the MS 110 in response to the SBC-REQ message. In this case, the first BS 120 checks the information on the modulation scheme and/or coding scheme available to the MS 110, included in the SBC-REQ message.
The SBC-REQ message and the SBC-RSP message are a kind of a medium access control (MAC) message that the MS 110 transmits/receives for basic capacity negotiation with the first BS 120.
In step 121, the MS 110 transmits a registration request (REG-REQ) message to the first BS 120. Upon receipt of the REG-REQ message, the first BS 120 detects the MS registration information included in the REG-REQ message, thereby registering the MS 110 with the first BS 120.
In step 123, the first BS 120 transmits to the MS 110 a registration response (REG-RSP) message with the registration information of the MS 110 registered in response to the receipt of the REG-REQ message. In this case, the first BS 120 transmits a primary management CID to the MS 110 along with the RNG-RSP message to exchange control signals for an initial access. For example, the primary management CID is assumed to be ‘110’.
In step 125, the MS 110 sets up a connection to the first BS 120 using the basic CID (=10) and the primary management CID (=110). The MS 110 can be additionally assigned a transport CID to exchange user data with the first BS 120.
Meanwhile, upon detecting the need for handover, the MS 110 transmits in step 127 a handover request (HO-REQ) message to the first BS 120. In step 129, the first BS 120 transmits a handover response (HO-RSP) message to the first BS 120 in response to the HO-REQ message. The HO-RSP message includes therein information on a target BS (e.g., second BS 130) to which the MS 110 will perform handover. The MS 110 determines if it will perform handover to the second BS 130 based on the information included in the HO-RSP message. If the MS 110 determines to perform handover to the second BS 130, the MS 110 transmits in step 131 to the first BS 120 a handover indication (HO-IND) message indicating that it will soon perform handover to the second BS 130, and then transmits in step 133 an RNG-REQ message to the handover target BS (i.e., second BS 130).
In step 135, the second BS 130 transmits an RNG-RSP message to the MS 110 in response to the RNG-REQ message. The RNG-RSP message includes a basic CID and a primary management CID for updating a CID of the MS 110. The second BS 130 can exchange its control data, or control signals, through the basic CID and primary management CID that it has assigned to the MS 110 and updated. For example, the basic CID is assumed to be ‘0’, and the primary management CID is assumed to be ‘430’. After receiving the RNG-RSP message from the second BS 130, the MS 110 performs a CID update (basic CID and primary management CID) using the CIDs included in the RNG-RSP message. Thereafter, in step 137, a connection is set up between the MS 110 and the second BS 130.
After performing the CID update, the MS 110 exchanges control data, or control signals, with the second BS 130, and can later perform user data transmission/reception through assignment of transport CID.
As described above, the CID is a value that each BS assigns to an MS that presently communicates with the corresponding BS, and when the MS switches from its current BS to a new BS, it should be assigned a new CID from the new BS.
In other words, the MS that performs handover or resumes its communication, is assigned a CID(s) from the target BS or its new BS, and then updates its CID, so it can perform data transmission/reception. Generally, however, the time required when the MS updates its CID(s) is, for example, 50 ms-100 ms.
As stated above, the MS intending to perform handover or to communicate with a new BS, must acquire the newly assigned CIDs, and the CID acquisition causes a time delay.